Various quaternary ammonium compounds are known in the art to possess antistatic properties. These quaternary ammonium componds are also known to be generally incompatible with anionic surfactants commonly employed in laundering compositions. The anionic surfactants attack and inactivate the quaternary ammonium compounds in the wash-water environment. Thus, larger amounts than desired of the fairly expensive quaternary ammonium compounds must be added to detergent compositions in order to avoid total inactivation in wash solution. It therefore would be highly beneficial, from a performance and economic standpoint, to be able to shield the quaternary ammonium compounds in the wash water, without disturbing their effectiveness as static control agents in the subsequent machine drying process.
Techniques known in the art for preserving the antistatic properties of the quaternary ammonium compounds, such as the prilling of the quarternary ammonium compound with organic dispersion inhibitors, as disclosed in U.S. Pat. No. 3,936,537, Baskerville et al, issued Feb. 3, 1976, incorporated herein by reference, and the agglomeration of that prill with certain water-soluble neutral or alkaline salts, using organic agglomerating agents, as disclosed in U.S. Pat. No. 4,141,841, McDonald, issued Feb. 27, 1979, incorporated herein by reference, while delivering improved static control and softening benefits over methods then known in the art, were only partially effective. Some of the quaternary ammonium compound continued to be inactivated by the anionic surfactants, and some of the prills continued to be broken up and dispersed in the wash water, preventing the efficient deposition of antistatic materials of an effective size range onto the fabrics to be treated. The above-described techniques still required the addition of larger quantities of the quaternary ammonium compound than necessary to achieve good static control in the absence of the detergent. Also, the conventional organic agglomerating agents, such as dextrin glue solutions, required in McDanald to agglomerate the prills with the salts could cause poor caking characteristics and flowability problems in the detergent product under certain conditions, making handling and packaging difficult at times.
The present invention, by contrast, teaches the deliberate pre-wash-water complexing of certain anionic components with the quaternary ammonium compounds to deliver superior static control at significantly reduced levels of antistatic material. The Baskerville et al and McDanald references attempted to avoid the interaction of anionic components with the quaternary ammonium compound upon which the present invention is based. Further, it has been discovered that water can act as the agglomerating agent and/or the complexing medium, while producing a product with at least equivalent caking characteristics, and even superior caking qualities under certain conditions. Thus, the organic agglomerating agents required in McDanald have been eliminated in the present invention, reducing material costs and eliminating extra processing and handling steps.
It is an object of the present invention to provide a particulate detergent additive composition which delivers static control and fabric-softening benefits to laundered fabrics while using a minimum amount of antistatic/softening agent.
It is also an object of the present invention to provide a detergent composition capable of concurrently laundering, softening, and imparting static control benefits to fabrics washed therewith and subsequently machine dried.